Technical Abstract:
Leucaena leucocephala is a drought tolerant legume containing a toxin, mimosine, that restricts its use as a forage. When ruminants are colonized with sufficient numbers of Synergistes jonesii, (a beneficial rumen bacteria capable of detoxifying mimosine) they can safely consume diets containing >50% leucaena. However in ruminants not consuming leucaena, the microbe may be absent or insufficient in number and toxicity can occur. For livestock producers to safely manage leucaena as a forage, they need to know the S. jonesii colonization status of their animals. Because the present method for culturing S. jonesii takes months to complete, we assessed the feasibility of using a more rapid polymerase chain reaction (PCR) method. Using purified DNA and primers specific to a non-homologous piece of S. jonesii DNA, S. jonesii could be detected at a level of 1.2 pg DNA. The specificity of the primers was confirmed when no PCR product was generated from bacterial DNA prepared from rumen, fecal, and saliva sample from cattle never exposed to leuceana. In all cases, S. jonesii could be detected from these samples when spiked with 1 ul of a pure culture of S. jonesii; however, the sensitivity was much better with rumen fluid and saliva than with feces. Synergistes jonesii was detected in rumen contents from a cow known to be colonized with S. jonesii (culture positive); however, detection of S. jonesii in feces was not reliable by either culture or PCR method.